| The upgrading and iteration of communication technology and the rapid change of the industry urgently need the rapid maturity and application of the fifth-generation mobile communication system technology,especially the 5G base station antenna covering the N77/N78/N79 frequency band.With the continuous expansion of 5G users,how to design and develop 5G base station antennas with performance characteristics such as bipolarization,miniaturization,broadband and high gain,and adapt to different communication scenarios is a technical point worthy of in-depth study and solution.Focusing on the demand of 5G base station antenna,the characteristics of dual polarization,broadband and miniaturization of antenna are studied,and the representative research results of various methods are deeply investigated.Based on the research results,aiming at the core trends of broadband,miniaturization and high gain,this thesis designs three dual polarization antennas applied to 5G base stations respectively.The main research contents are summarized:1.A miniaturized broadband antenna covering 5G band is proposed.The designed square radiator and V-shaped feeding branches are printed on the upper and lower sides of the dielectric board respectively.A pair of mutually orthogonal microstrip baluns are vertically placed under the dielectric plate for balanced feeding and impedance matching.Four V-shaped feeding branches are connected at the upper end of the balun short circuit wall to enhance the coupling and expand the bandwidth.The planar patch antenna with shared dipole arm generates±45°polarization through vector synthesis,covering the impedance bandwidth of 3.2–6.2 GHz reflection coefficient-15 d B,realizing 63%relative bandwidth.The processing test results show that the antenna has low cross polarization,stable radiation pattern and gain in the operating frequency band.This design provides a new scheme for the development of broadband miniaturization.2.A low profile dual polarization antenna based on AMC structure is designed.The radiator of the antenna is a cross dipole,which is miniaturized by loading two open branches at the end of the ring dipole.The planar cross dipole and Y-shaped feeding branches are printed on both sides of the dielectric board respectively.The two coaxial feeders are connected with the Y-shaped feeder branch,which is used to balance the feed and impedance matching.In addition,it also plays the role of supporting the radiator.The non via patch AMC structure is adopted to reduce the height of the antenna.The Y-shaped microstrip stub feeding structure connected with the coaxial line can be unrestricted,so it is easier to integrate with AMC structure.The size of the designed micro base station antenna unit is 0.24λ_L×0.24λ_L×0.08λ_L.It covers reflection coefficient-15 d B impedance bandwidth of 3.12-3.83 GHz.At the same time,it realizes the isolation between ports of more than 25 d B and the gain of7±0.3 d Bi in this operating frequency band.3.According to the pattern superposition technology,a high gain antenna unit based on vertically arranged two-element array is designed.The dipole with a height of one quarter of the wavelength is the main radiator,and the active dipole structure loaded at one quarter of the wavelength from the upper end is the secondary radiator.By simultaneously exciting the primary and secondary radiators with different amplitude and phase signals,the beam width is reduced and the antenna gain is improved.The gain of the antenna is increased from8 d Bi to 10 d Bi in the operating frequency band of 3.26-4.12 GHz,and the maximum gain is up to 11 d Bi.Based on the designed antenna unit,an array application example is given,and the simulation results show that the array has good radiation characteristics in N77 band. |
PDF Full Text Request